github: add Docker build verification workflow

Add GitHub workflow to detect regressions in docker/dev/Dockerfile by:
- Building a container image on Dockerfile changes in PRs
- Running test suite against the built image in dev mode
- Using clang++ compiler with C++23 standard

This helps catch build issues and incompatibilities early in the
development process.

Refs scylladb#2656
Signed-off-by: Kefu Chai <[email protected]>

.github/workflows/docker.yaml

@@ -0,0 +1,35 @@
+name: Verify Dockerfile Build
+
+on:
+  pull_request:
+    paths:
+      - 'docker/dev/Dockerfile'
+      - 'install-dependencies.sh'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+
+jobs:
+  build:
+    timeout-minutes: 20
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          sparse-checkout: |
+            docker/dev/Dockerfile
+            install-dependencies.sh
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: docker/dev/Dockerfile
+          push: false
+          cache-from: type=gha
+          cache-to: type=gha,mode=max